A photo-voltaic (PV) battery directly converts solar energy into electric energy. The PV battery is widely applied because of advantages such as that the PV battery is not limited by resource distribution areas, electricity can be generated near a location at which electricity is used, a time taken to obtain energy is short, and energy quality is high.
A PV inverter (an inverter for short below) is an inverter that is powered by a PV battery. A main function of the inverter is to convert a direct current of a PV battery into an alternating current. The PV battery supplies power to the inverter in a form of charging a bus capacitor, and a voltage across the bus capacitor is a bus voltage, for example, the bus voltage may be used to supply power to an auxiliary power supply circuit of the inverter and an inverter circuit of the inverter, where the auxiliary power supply circuit may supply auxiliary power to components, for example, the inverter circuit, of the inverter. At the moment when the PV battery is connected to the inverter, the auxiliary power supply circuit of the inverter is not started up yet. In this case, the PV battery charges the bus capacitor in a form of an approximate constant current source. When the bus voltage reaches a startup voltage of the auxiliary power supply circuit, the auxiliary power supply circuit is started up. In this process, the PV battery continuously charges the bus capacitor until the bus voltage rises to an open circuit voltage of the PV battery (however, because there is a slight loss on the inverter, the PV battery generally stops charging when the bus voltage rises slightly less than the open circuit voltage of the PV battery). It can be known that the bus voltage is associated with the open circuit voltage of the PV battery.
Low-voltage components are included inside the inverter. To prevent the low-voltage components from getting burnt out, an operating voltage of the inverter should not be excessively large, for example, the bus voltage should not be excessively large and further the open circuit voltage of the PV battery should not be excessively large either. The open circuit voltage of the PV battery is limited and a charging speed of the bus capacitor is limited. As a result, the auxiliary power supply circuit of the inverter and the inverter circuit of the inverter need a relatively long time to be started up. Therefore, a startup speed of the inverter is relatively slow.